The present invention relates to microstructures, particularly to electromechanical micromechanisms, and more particularly to microgrippers for use in catheter-based interventional therapies or remote micro-assembly applications.
Microactuators for remote and precise manipulation of small objects is of great interest in a wide variety of applications. The design and development effort of such microgripper devices would be useful in the art as such will apply to general microfabrication techniques and establish the infrastructure for microengineering efforts including robotics, microtechnology, prevision engineering, defense, energy, and biomedical research, as well as use in medical applications, such as for catheter-based interventional therapies and remote assembly or use of micromechanical system.
When a portion of a blood vessel weakens, it bulges and forms a aneurysm, which is one of the main reasons for strokes as the vessel finally collapses and opens. These aneurysms have traditionally been treated by surgery, where the surgeon will have to open up the area of repair before attempting to surgically repair the aneurysm by clipping it. However, many aneurysms are at critical locations such as in the brain and are either difficult and risky to operate on or it is simply impossible. For the last 20 years, pioneering doctors have used interventional neuroradiology techniques to aid the treatment of brain aneurysms. Long (1-2 meters) and narrow (i.e. 250 .mu.m to 500 .mu.m) catheters are pushed through the arteries in the groin up to the brain to reach the aneurysm. Existing catheter-based interventional instruments rely on simplistic and usually singular means of actuation. These techniques, including balloon angioplasty, are well-established for large vessel treatments such as in the heart. It is crucial that in order to extend this medical practice into the smaller vessels such as those in the brain, the catheter-based tools must be miniaturized. In the most recent method, platinum coils were selected to fill up the aneurysms due to its ability to fill up irregular shapes and its resistance to electrolysis in the vessels when it is charged. The coils are either pushed through the catheter to the aneurysm by a guide wire or released by the electrolytic dissolution of a solder joint between the guide wire of the catheter and the therapeutic device, which for neurological treatments are approximately 250 .mu.m or less in diameter. Although the charging of the coil causes electrothrombosis around the coil, the time required to release the coil is long (4 mins to 1 hr) and many coils are usually needed to fill up a regular size aneurysm. The extent to which the dissolved material affects the body is unknown and electrolysis soldering requires long terms of current in the brain and sometimes is simply unreliable. These difficulties present potential life-threatening problems to the patient for the surgeon and clinician.
Thus, there is a need for a micromechanism which can fit into a 250 .mu.m diameter area and which would enable the physician to release and retrieve the coils or other therapy once it is released at the wrong time or location. The present invention satisfies this need by providing a micromechanical release mechanism by which this procedure becomes a safer and more reliable alternative to surgery, and which can fit into blood vessels of the brain, a 250 .mu.m diameter area. The electromechanical microstructures, including microgrippers, can be fabricated using known IC silicon-based techniques or precision micromachining, or a combination of these techniques. While the invention has application in various areas requiring a remotely actuated microgripper, it has particular application in catheter-based interventional therapies.